Fluorescent pigments

ABSTRACT

A fluorescent pigment consisting of N-substituted iminocoumarins of the general formula I, ##STR1## wherein X 1  is a cyano group, a carboxamido group or an aryl or a heteroaryl radical linked directly or through a --CO or --SO 2  group, 
     X 2  is an amino group, hydroxy group or an alkoxy group and when it is an amino group, may carry an optionally substituted alkylene or alkylidene group bound in ortho position to the nitrogen atom and in para position with respect to the coumarin oxygen atom, 
     X 3  is a hydrogen atom, a halogen atom or a cyano group and 
     X 4  is a functionally converted carboxyl groups. The new dyestuffs dye polyester fiber in orange or red shades with good fastness.

The present invention relates to a new class of luminous pigments, aprocess for their manufacture, their use in colouring organic materials,especially the use of such pigments as are sparingly soluble in water asdisperse dyestuffs for dyestuffs for dyeing and printing hydrophobicfibres, their use as organic dye lasers and as industrial products andthe material dyed or printed with new pigments.

The new, fluorescent pigments, which have been found, are N-substitutediminocoumarin derivatives of the general formula I ##STR2## wherein X₁is a cyano group, a carboxamido group or an aryl or a heteroarylradical, linked directly or through --CO or SO₂ group,

X₂ is an amino group, hydroxy group or an alkoxy group, and when it isan amino group, may carry an optionally substituted alkylene oralkylidene group bound in ortho position to the nitrogen atom and inpara position to the coumarin oxygen atom,

X₃ is a hydrogen atom, a halogen atom or a cyano group and

X₄ is a functionally converted carboxyl group.

The carboxamido group X₁ is a group --CONHR wherein R is a hydrogenatom, an optionally substituted lower alkyl group, especially thosesubstituted by hydroxy or acyloxy group, a cycloalkyl group, an aryl ora heteroaryl group.

The term lower referred to in this application pertaining to radicals orgroups refer to those radicals or groups containing not more than 6carbon atoms.

The aryl radicals are especially phenyl or naphthyl radicals optionallysubstituted by groups such as nitro or optionally substituted amino,halogen atoms e.g. fluorine, chlorine and bromine, or lower alkyl suchas methyl, ethyl, n-propyl, isopropyl or n-or iso butyl radicals, orlower alkoxy, e.g. methoxy and ethoxy radicals.

The heteroaryl radicals may be mono or bicyclic heteroaryl radicals e.g.pyridyl, thienyl, furyl, triazolyl, benzimidazolyl, benzoxazolyl,benzthiazolyl, quinoxalinyl or quinazolyl radicals. Such radicals mayalso carry substituents such as lower alkyl, lower alkoxy radicals orhalogen atoms.

The radical X₂ representing an amino group may also represent a mono orpreferably disubstituted amino group. The substituents of the aminogroup are aliphatic hydrocarbon radicals especially lower alkyl radicalswhich may be optionally substituted for example by hydroxyl or nitrilegroups, lower alkoxy groups with preferably 1 to 4 carbon atoms, acyloxygroups, phenoxy groups or halogen, such as chlorine or bromine. Thefollowing should be mentioned individually, methyl, ethyl, propyl,butyl, hexyl, β-ethylhexyl, β-hydroxyethyl or β-hydroxypropyl,γ-hydroxypropyl, ω-hydroxyhexyl, β-methoxyethyl, γ-methoxypropyl,β-ethoxyethyl, γ-ethoxypropyl, γ-isopropoxypropyl, γ-butoxypropyl,β-aminoethyl, γ-dimethylaminopropyl, γ-dibutylaminopropyl orω-aminohexyl and the radicals of the formulae ##STR3## or an alkylene oralkylidene group which is bound to the benzene nucleus in orthopositionto the N-atom and in para position to the coumarin oxygen atom e.g., agroup of the formula --CH₂ CH₂ CH₂ -- or ##STR4## or other propylene orpropylidene groups substituted by lower alkyl groups or hydroxy groups.

The nitrogen atom of the amino group may form part of a heteroringconjointly with the substituents present. In such cases the ring ispreferably 5-membered or 6-membered and not aromatic; it can be, forexample, the pyrrolidine or piperidine ring, and if this ring includes afurther hetero-atom, for example, the morpholine radical or a piperazinering which is optionally N'-substituted, especially by alkyl or acylgroups, such as the N'-acetylpiperazine radical, or a radical of theformula ##STR5## The group X₄ is preferably a carboxylic ester groupespecially ester of a lower alkanol such as methanol, ethanol orpropanol, or a cyano group.

These new compounds of formula (I) are obtained by reactingiminocoumarins of general formula (II) with ethylene derivatives##STR6## of the formula III. In formulae (II) and (III), X₁, X₂, X₃ andX₄ have the same meaning as given under formula (I) and Y represents aleaving group, such as an alkoxy especially a lower alkoxy or a cyanogroup or a halogen atom e.g. chlorine, bromine or a fluorine atom.

The iminocoumarins which are to be used in accordance with the inventioncan be obtained by the known procedure of Knoevenagel condensationbetween salicylaldehydes of formula IV and active methylene compounds ofthe formula V ##STR7## where X₁ and X₂ have the meanings given earlier.

Examples of suitable salicyldehyde derivatives are:

4-Dimethylaminosalicylaldehyde, 4-diethylamino salicylaldehyde,4-ethylamino salicylaldehyde, 4-N-ethyl-N-β-acetoxyethylsalicylaldehyde,4-N,N-di(β-acetoxyethyl) aminosalicylaldehyde, 4-methoxysalicylaldehyde,resorcilaldehyde.

The following examples of active methylene compounds may be mentioned.

Malodinitrile, cyanoacetamide, cyanoacetaniline,p-chlorocyanoacetaniline, p-methoxycyanoacetaniline,p-nitrophenylacetonitrile, p-chlorophenylacetonitrile,p-methoxyacetonitrile, 2-cyanomethylthiophene, 2-cyanomethylbenzimidazole, 2-cyanomethyloxazole, 2-cyanomethylbenztriazole,2-cyanomethylquinazolone, 2-cyanomethylquinazoline etc.

Reaction between the iminocoumarins and the ethylene derivatives may becarried out in suitable organic solvents in the temperature range ofroom-temp. to 150°.

Examples of suitable solvents are hydrocarbons, such as benzene, tolueneor xylenes, halogenated hydrocarbons, such as carbon tetrachloride,sym-tetrachloroethane, chlorobenzene or o-dichlorobenzene, ornitrohydrocarbons, such as nitromethane or nitrobenzene, ethers such astetrahydrofuran, dioxane, dibutylether, esters, amides, nitriles such asethyl acetate, dimethylformamide, acetonitrile or even dimethylsulfoxidecan be used as solvent.

It is not expedient to isolate the iminocoumarins in all cases; insteadthe ethylene derivative is added to the reaction mixture containing thesalicylaldehyde derivative and the active methylene compound.

A less general alternative procedure for the preparation of the pigmentsof the formula I (with X₁ =X₄ =CN, X₂ =N R₁ R₂ and X₃ =H) consists intreating m-dialkylamino phenol with two mole-equivalents of 1-chloro-2,2-dicyanoethylene in a suitable solvent, such as chlorobenzene ortetrahydrofuran, at room-temperature.

The new pigments usually crystallize out of the reaction mixture oncooling and are easily isolated by filtration or are isolated by theremoval of the solvent if necessary by steam distillation. If need be,they can be further purified by crystallization from high boilingorganic solvents, such as dimethylformamide, chlorobenzene oro-dichlorobenzene. The solution of these pigments in organic solventssuch as acetone, alcohol, chlorobenzene, dimethylformamide and ethylacetate exhibit strong fluorescence in daylight and in ultravioletlight.

The new water-insoluble or sparingly soluble pigments are particularlysuitable for dyeing textile material such as for example, acrylic oracrylo nitrile fibres, polyacrylonitrile fibres and copolymers ofacrylonitrile and other vinyl compounds, such as acrylic esters,arylamides, vinylpyridine, vinyl chloride or vinylidene chloride,copolymers of dicyanoethylene and vinyl acetate, and of acrylonitrileblock copolymers, fibres composed of polyurethanes, polyolefines, suchas polypropylene modified by a base, polypropylene modified with nickelor unmodified polypropylene, cellulose triacetate and cellulose21/2-acetate and particularly fibres composed of polyamides, such asnylon 6, nylon 6,6 or nylon 12, and of aromatic polyesters, such asthose of terephthalic acid and ethylene glycol or1,4-dimethylcyclohexane, and isophthalic acid and ethylene glycol.

The new dyestuffs which are free from sulpho and quaternised nitrogenatoms are particularly suitable for dyeing textile material consistingof high molecular organic esters, such as cellulose 21/2-acetate orcellulose triacetate, but particularly for dyeing or printing textilematerial of polymeric esters of aromatic polycarboxylic acids withpolyhydric alcohols, above all polyethylene glycol terephthalate orpolycyclohexanedimethylol terephthalate or textured polyesters fibressuch as, for examples, DIOLEN LOFT^(R) (Vereinigte Glazstoff-Werke),CRIMPLENE^(R) (ICI), and SCHAPIRA^(R) (Hoechst). The dyestuffs can,however, also be used for dyeing synthetic polyamide fibres, such aspolyhexamethylene adipamide, polycaprolactam or polyamino undecanoicacid, and for dyeing polyolefines, especially polypropylene fibres. Theybelong to the class of the disperse dyestuffs, such as are defined, forexample, in the Colour Index.

In addition, depending on the composition, they are suitable for bulkdyeing or pigmenting lacquers, oils and waxes and cellulose derivatives,especially cellulose esters, such as cellulose acetate.

The new dyestuffs can be used also for laser applications.

The following examples may be mentioned of dispersing agents of thenon-ionic group which can be used with advantage: addition products of 8mols of ethylene oxide to 1 of p-tert. -octylphenol, of 15 or 16 mols ofethylene oxide to castor oil, and of 20 mols of ethylene oxide to thealcohol C₁₆ H₃₃ OH, ethylene oxide addition products withdi-phenylethyl-phenols, polyethylene oxide tert.-dodecylthioethers,polyamide polyglycol ethers or addition products of 15 or 30 mols ofethylene oxide to 1 mol of the amine C₁₂ H₂₅ NH₂ or C₁₈ H₃₇ NH₂.

The following anionic dispersing agents may be mentioned: sulphuric acidesters of alcoholic of the aliphatic series with 8 to 20 carbon atoms,of the ethylene oxide adducts of the corresponding fatty acid amides, orof alkylated phenols with 8 to 12 carbon atoms in the alkyl radical;sulphonic acid esters having alkyl radicals with 8 to 20 carbon atoms;sulphation products of unsaturated fats and oils; phosphoric acid estershaving alkyl radicals with 8 to 20 carbon atoms; fatty acid soaps andalso alkylarylsulphonates, condensation products of formaldehyde withnaphthalenesulphonic acid and ligninsulphonates.

Suitable cationic dispersing agents are quaternary ammonium compoundscontaining alkyl or aralkyl radicals with 8 to 20 carbon atoms.

In addition to the dispersing agents, the dyestuff preparations can alsocontain organic solvents, especially solvents which boil above 100° C.and which are preferably miscible with water, such as monoalkyl glycolethers and dialkyl glycol ethers, dioxane, dimethylformamide ordimethylacetamide, tetramethylenesulphone or dimethylsulphoxide.Dyestuff, dispersing agent and solvent can advantageously be ground withone another.

The polyester fibres are dyed from an aqueous dispersion with thedyestuffs according to the invention which are sparingly soluble inwater, according to processes which are customary for polyestermaterials. Polyesters of aromatic polycarboxylic acids with polyhydricalcohols are preferably dyed at temperatures of above 100° C. and underpressure. The dyeing can, however, also be carried out at the boilingpoint of the dye bath in the presence of dyestuff carriers, for examplealkali metal phenylphenolates, polychlorobenzene compounds or similarauxiliaries, or can be carried out by the padding process and subsequenthot after-treatment, for example thermofixing at 180° to 210° C.Cellulose 21/2-acetate fibres are preferably dyed at temperatures of 80°to 85° C., while cellulose triacetate fibres and synthetic polyamidefibre material are dyed advantageously at the boiling point of the dyebath. When the last-mentioned kinds of fibres are dyed, the use ofdyestuff carriers is superfluous.

The dyeings obtained according to the present process can be subjectedto an after-treatment, for example by heating with an aquous solution ofa non-ionic detergent.

The textile materials mentioned are also printed according to thecustomary methods, for example by printing the goods with the printingpaste containing, in addition to the dyestuff and the dyeingaccelerator, thickeners and customary additives, such as, for example,urea and subsequently fixing the dyestuff by steaming for 15 minutes at100° to 130° C.

It is further possible, for example, to dye synthetic fibres, such aspolyesters and polyamides, in organic solvent liquors, such as a mixtureof perchloroethylene and dimethylformamide or methanol, or inperchloroethylene alone, or perchloroethylene-water emulsions.

The new iminocoumarin derivatives of the formula I which can be used asdisperse dyestuffs are very well absorbed on the above-mentionedhydrophobic organic fibre material, particularly on polyethylene glycolterephthalate fibres and, on this fibre material, they yield pure, full,yellow, orange, red and bluish red dyeings with a high brilliance andfluorescence. In addition, the dyeings are very fast to washing,fulling, rubbing, perspiration, solvents, decatising, light andsublimation.

In the following examples, unless otherwise stated, parts denote partsby weight, percentages denote percentage by weight and temperatures arein degrees centigrade.

EXAMPLE 1

12.2 parts of ethoxymethylenemalodinitrile are gradually added to aboiling solution of 33.7 parts of7-diethylamino-3-(p-nitrophenyl)-2-imino coumarin in 300 parts ofchlorobenzene in about 10 minutes. The deep red brown mixture is thengently refluxed for 15 minutes. On cooling, dyestuff of the formula##STR8## separates as red brown needles; it is filtered, washed withhexane and dried. After one crystallisation from chlorobenzene it meltsat 281°-82° with slight decomposition. Its solutions in organic solventsare red with intense orange fluorescence (λ_(max) 505 and 535 nm withε_(max) 35,000 and 39,300 respectively). It dyes polyester a brilliantred shade with excellent fastness.

The iminocoumarin derivative required for above procedure is prepared asfollows:

A mixture of 19.3 parts of 4-diethylaminosalicylaldehyde, 16.2 parts ofp-nitrophenylacetonitrile, 0.3 part piperidine and 400 parts of ethanolis refluxed for 3 hours. On cooling iminocoumarin of the formula##STR9## separates as shining red brown plates, m.p. 180°-85° (dec.).

PROCEDURE (B)

A mixture of 19.3 parts of 4-diethylaminosalicylaldehyde, 16.2 parts ofp-nitrophenylacetonitrile, 0.3 part of piperidine and 100 parts ofchlorobenzene is refluxed for 30 minutes. 12.2 Parts of ethoxymethylenemalodinitrile are then added to the hot mixture and the resulting deepred brown mixture is further refluxed for 10 minutes. On cooling, theproduct, indentical with one described in para 1 of the procedure A,separates as brick-red needles.

EXAMPLE 2

Using 16.9 parts of ethyl 2-cyano-3-ethoxyacrylate in place of 12.2parts of ethoxy methylenemalodinitrile in Procedure A of Example 1, oneobtains the dyestuff of the formula ##STR10## as orange red crystals; itdyes polyesters a brilliant orange shade by the thermofix procedure.

EXAMPLE 3

In place of 33.7 parts of the iminocoumarin used in Procedure A ofExample 1, there are used 33.2 parts of7-diethylamino-2-(2'-benzimidazolyl)-iminocoumarin, whereby one obtainsa similar dyestuff of the formula ##STR11## When applied by thermofixprocedure from its aqueous dispersion, the dyestuff gives on polyester afluorescent red shade of good fastness properties.

The imino-coumarin used in this Example is prepared as follows:

A mixture of 19.3 parts of 4-diethylaminosalicylaldehyde, 13.7 parts of2-cyanomethylbenzimidazole, 0.3 part of piperidine and 300 parts ofmethanol is stirred at room temperature for 10 to 12 hours. Thecrystalline yellow precipitate of the iminocoumarin ##STR12## isfiltered, wahsed with little methanol and dried.

EXAMPLE 4

12.2 parts of ethoxymethylenemalodinitrile are added at once to aboiling mixture of 33.5 parts of anilide of7-diethylaminoiminocoumarin-3-carboxylic acid and 300 parts ofchlorobenzene. The resulting bright red solution is simmered for 2 to 3minutes and cooled. The separated red prisms of the dyestuff ##STR13##are filtered, washed with hexane and dried. It gives a bright orangeshade with good fastness properties on polyester.

The iminocoumarin used in this Example is prepared by a process similarto one described for the preparation of anilide of cyanoacetic acid inplace of 15.7 parts of 2-cyanomethylbenzimidazole; it is obtained asgreenish yellow crystals, m.p. 200°-204°.

EXAMPLE 5

A solution of 12.8 parts of tetracyanoethylene in 150 parts oftetrahydrofuran is added gradually to a stirred mixture of 33.2 parts of7-diethylamino-3-(2'-benzimidazolyl) iminocoumarin and 150 parts oftetrahydrofuran at room temperature. The yellow colour of the mixturethereby changes to violet brown and violet brown crystals with metallicluster soon begin to separate. The mixture is stirred at roomtemperature for one-half hour and the violet brown crystalline product,which corresponds to the structure ##STR14## is filtered, washed withsmall amount of tetrahydrofuran and dried.

It gives on polyester a violet shade.

EXAMPLE 6

(i) 10.8 parts of ethyl chloroformate are added gradually to a solutionof 13.9 parts of m-nitrophenol in 40 parts of water containing 4 partsof sodium hydroxide at 20°-22°. After the addition is over the mixtureis stirred at 20°-22° for 30 minutes and the precipitated colourlesscrystalline product ##STR15## is filtered, washed neutral and dried;after one recrystallization from alcohol it melts at 53°-54°.

(ii) 21.1 Parts of the above ester are dissolved in 100 parts of alcoholand reduced catalytically at atmospheric pressure in presence of 5%palladium on charcoal. After filtering off the catalyst, the reducedproduct ##STR16## is recovered from the filtrate as colourless viscousoil and is used for the next step without further purification.

(iii) A mixture of 18.1 parts of the above reduced product, 100 parts ofabsolute ethanol and 8 parts of Raney nickel catalyst is refluxed withstirring for 7 hours. After cooling, the catalyst is filtered and thecrude secondary amine ##STR17## is recovered from alcohol filtrate andpurified by fractional distillation under high vacuum (b.p. 175°-80°/1mm).

(iv) 8.0 Parts of liquified ethylene oxide are added to a mixture of21.0 parts of the above secondary amine, 50 parts of acetic acid and 50parts of water with stirring at room-temperature. The mixture is thenstirred in a closed vessel at room temperature until thin layerchromatogram of the reaction mixture indicates completion of thereaction (3 to 5 hours). The solvent is then removed completely from thereaction mixture by evaporation under reduced pressure and the crudeproduct ##STR18## obtained as viscous oil is heated with 30 parts ofacetic anhydride on a boiling water-bath for 1 hour. Excess aceticanhydride and acetic acid formed are then removed by evaporation underreduced pressure and the crude acetyl derivative obtained as cleanviscous oil ##STR19## is used for the next step without furtherpurification.

(v) 29.5 Parts of the above acetyl derivative are added to a solution of23.0 parts of phosphorus oxychloride in 30 parts of dimethylformamide atroom temperature. The temperature of the mixture is then raised to60°-65° and it is stirred at this temperature for 5 hours. It is thenpoured into 500 parts of cold water and the resulting aqueous mixture isneutralized to pH 5-6 by addition of sodium acetate, whereby the formylderivative ##STR20## separates as an oil. It is separated from theaqueous mixture by extraction with chloroform and is used withoutfurther purification for the next step.

(vi) 25.0 Volume parts of 10 N caustic potash solution are added to asolution of 32.3 parts of the above aldehyde in 300 parts of methanoland the mixture is refluxed on boiling water-bath for 30 minutes. Aftercooling 25.0 parts of conc. hydrochloric acid are added to the mixtureand the precipitated potassium chloride is filtered off. From thefiltrate, solvent is removed completely and the hydrolyzed product##STR21## is extracted from the residue with 150 parts of boilingchlorobenzene. The chlorobenzene extract is then treated with 16.2 partsof p-nitrophenyl acetonitrile, and 9.3 parts of piperidine and themixture is then refluxed for 15 minutes. The resulting yellow-brownmixture containing the iminocoumarin derivative ##STR22## is treatedwith 12.2 parts of ethoxymethylene malodinitrile and the resulting deepred solution is simmered for 1-2 minutes. On cooling, the dyestuff ofthe formula ##STR23## separates out as brick-red crystals; it isfiltered, washed with petroleum ether and dried. It dyes polyester abrilliant, fluorescent orange shade.

EXAMPLE 7

A mixture of 5.0 parts of the dyestuff of Example 6 and 25.0 parts ofacetic anhydride is heated on boiling water bath for 1 hour and pouredinto 250 parts of cold water. The brick red precipitate of the dyestuff##STR24## that separates on standing is filtered, washed and dried. Italso dyes polyester, an attractive, fluorescent, orange shade.

EXAMPLE 8

(i) A mixture of 18.1 parts of ethyl m-aminophenoxyformate and 8.5 partsof benzylbromide is stirred on a boiling water bath for 30 minutes.After cooling the mixture is diluted with 150 parts of benzene andstirred until the precipitation of the hydrobromide of ethylm-aminophenoxyformate is complete. The crystalline precipitate isfiltered off and the secondary amine ##STR25## is recovered from thefiltrate as colourless viscous oil.

(ii) 8.0 Parts of liquefied ethyleneoxide are added to a mixture of 27.1parts of the above secondary amine, 100 parts of acetic acid and 100parts of water and the mixture is stirred in a closed vessel for 22 to24 hours. Excess ethyleneoxide and the solvents are then removed byevaporation under reduced pressure from the reaction mixture and theresidual tertiary amine ##STR26## is heated with 30 parts of aceticanhydride on a boiling water-bath for 1 hour. After removing excessacetic anhydride and acetic acid formed from the reaction mixture byevaporation under reduced pressure, 35.7 parts of the resulting acetylderivative ##STR27## are formylated with a mixture of 23.0 parts ofphosphorus oxychloride and 30 parts of dimethylformamide as described inExample 6. The crude formyl derivative ##STR28## obtained as viscous,brownish oil is used without further purification.

(iii) A solution of 38.5 parts of the above aldehyde in 300 parts ofmethanol is refluxed with 25.0 volume parts of 10 N caustic potash for30 minutes. After cooling 25.0 parts of conc. hydrochloric acid areadded to the mixture and the precipitated potassium chloride is filteredoff. From the filtrate, methanol is removed completely and thehydrolysed product ##STR29## is extracted with 150 parts of boilingchlorobenzene. Chlorobenzene extract is then treated with 16.2 parts ofp-nitrophenylacetonitrile in presence of 0.3 parts of piperidine andrefluxed for 15 minutes to yield a yellow brown solution of theiminocoumarin. ##STR30## The hot solution of the latter is then treatedwith 12.2 parts of ethoxymethylenemalodinitrile and the resulting deepred solution on cooling yields the dyestuff of the formula ##STR31## asbrick-red crystals; it also gives fluorescent orange shade on polyester.

EXAMPLE 9

A mixture of 5.0 parts of the dyestuff of Example 8 and 20 parts ofbenzoylchloride is refluxed with stirring for 5 minutes. On cooling,dyestuff of the formula ##STR32## separates as brick-red crystals; it isfiltered, washed with ether and dried. It also gives a deep, brilliantorange red on polyester.

EXAMPLE 10

16.0 Parts of liquefied ethyleneoxide are added to a mixture of 18.1parts of ethyl m-aminophenoxyformate, 50.0 parts of acetic acid and 50.0parts of water at room temperature and the mixture is stirred in aclosed vessel for 16 hours. Solvent is then completely removed and theresidual oily product ##STR33## is acetylated by heating with 50.0 partsof acetic anhydride on boiling water-bath for 30 minutes. After stirringoff excess acetic anhydride and acetic acid from the reaction mixture,the bisacetylated product ##STR34## is formylated as described inExample 6. 38.1 Parts of the aldehyde ##STR35## are then hydrolyzed byboiling its methanolic solution with 30 vol.parts of 10 N caustic potashsolution. The hydrolized product ##STR36## is taken up in 150 parts ofchlorobenzene and treated sucessively with 16.2 parts ofp-nitrophenylacetonitrile (in presence of 0.3 parts piperidine) and 12.2parts of ethoxymethylenemalodinitrile, as described in para (vi) ofExample 6, to yield the dyestuff of the formula ##STR37## as deep violetred crystals.

EXAMPLE 11

A mixture of 10.0 parts of the dyestuff of Example 10, 30 parts ofacetic anhydride and 30 parts of acetic acid is heated on boilingwater-bath for 30 minutes. On cooling, the dyestuff of formula ##STR38##separates as red crystals; it is filtered, washed with little aceticacid and dried. It gives a brilliant orange red shade on polyester.

EXAMPLE 12

(i) A mixture of 18.1 parts of ethyl m-aminophenoxyformate and 8.5 partsof ethyl 3-bromopropionate on a boiling water-bath for 40 minutes. Aftercooling, the reaction mixture is stirred with 100 parts of benzene andthe precipitated hydrobromide of ethyl m-aminophenoxyformate is filteredoff. Removal of solvent from the filtrate gives the secondary amine ofthe formula ##STR39## as colourless, viscous oil.

(ii) 8.0 Parts of ethyleneoxide are added to a mixture of 28.1 parts ofthe above secondary amine, 100 parts of acetic acid and 100 parts ofwater and the mixture is stirred in a closed vessel at room temperaturefor 16 hours. On removing the solvent from the reaction mixture, thehydroxy ethylated product ##STR40## is obtained as colourless viscousoil, which is then heated with 50.0 parts of acetic anhydride to yieldthe acetyl derivative ##STR41##

(iii) 36.7 Parts of the above tertiary amine are added to a mixture of23.0 parts of phosphorusoxychloride and 30.0 parts of dimethylformamide.The mixture is heated to 60°-65° with stirring for 5 hours and worked upas described in example 6 to yield the formyl derivative of thestructure ##STR42## as viscous oil.

(iv) A solution of the above aldehyde in 300 parts of methanol isrefluxed with 30.0 vol.parts of 10 N caustic potash for 30 minutes.After cooling, the mixture is treated with 30.0 parts of concentratedhydrochloric acid, precipitated potassium chloride is filtered off andthe residue of the hydrolyzed product ##STR43## obtained after removalof the solvent form the filtrate is extracted with 150 parts of boilingchlorobenzene. Chlorobenzene extract is then refluxed with 15.7 parts of2-cyanomethyl benzimidazole, 0.3 part of piperidine for 15 minutes andthe resulting solution containing the iminocoumarin derivative ##STR44##is treated with 12.2 parts of ethoxymethylenemalodinitrile and refluxedfurther for 5 minutes. On cooling, the dyestuff of the structure##STR45## separates out as deep red crystals; it gives bright reddyeings on nylon and polyester.

EXAMPLE 13

(i) A mixture of 18.1 parts of ethyl m-aminophenoxyformate, 6.0 parts ofacrylonitrile and 20 parts of phenol is heated in a closed vessel at100°-105° for 20 hours. Phenol is removed from the reaction mixture bydistillation under high vacuum and the residual monocyanoethylatedproduct ##STR46## is used for the next step without any purification.

(ii) A mixture of 23.4 parts of the secondary amine described above, 8.0parts of liquefied ethyleneoxide, 100 parts of acetic acid and 100 partsof water is stirred in a closed vessel at room temperature for 5 hours.The hydroxyethylated product ##STR47## recovered from the reactionmixture by the complete removal of solvent is then acetylated by heatingwith 50 ml of acetic anhydride on boiling water-bath for 30 minutes.32.0 Parts of the acetyl derivative ##STR48## are then formylatedaccording to the procedure described in example 6 and the formylderivative ##STR49## is hydrolysed according to procedure used inexample 6 to yield the salicylaldehyde derivative ##STR50## solution in150 parts of chlorobenzene. The latter is then treated with 16.2 partsof p-nitrophenylacetonitrile 10.3 parts of piperidine and refluxed for15 minutes. The resulting solution of iminocoumarin ##STR51## is treatedwith 12.2 parts of ethoxy of ethoxymethylene malodinitrile, in usualmanner, to yield the dyestuff of the structure ##STR52## as brick-redcrystals. It gives a bright yellow-orange shade on polyester.

EXAMPLE 14

A mixture of 19.3 parts of 4-diethylaminosalicylaldehyde, 12.3 parts of2-thienylacetonitrile, 0.3 part piperidine and 100 parts ofchlorobenzene is refluxed for 12 minutes. The hot solution, containingthe iminocoumarin derivative ##STR53## is treated with 12.2 parts ofethoxymethylenemalodinitrile and the resulting deep reddish violetsolution is simmered for 2 to 3 minutes. On cooling, dyestuff of theformula ##STR54## separates as dark violet crystals. It gives a brightred shade on polyester.

EXAMPLE 15

Using 11.8 parts of 3-pyridylacetonitrile, in place of2-thienylacetonitrile in the above procedure (Example 14), one obtainsthe dyestuff of the formula ##STR55## It dyes polyester an attractivefluorescent, pink shade.

EXAMPLE 16

Using 11.8 parts of 2-pyridylacetonitrile in place of2-thienylacetonitrile and 16.9 parts of ethyl 2-cyano-3-ethoxyacrylatein place of 12.2 parts of ethoxymethylenemalodinitrile, one obtains thedyestuff of the formula ##STR56## as red crystals. It gives afluorescent orange-red shade on polyester.

EXAMPLE 17

If in place of 2-thienylacetonitrile in the procedure of example 14,there are used 15.2 parts of p-chlorobenzylcyanide, one obtains thedyestuff of formula ##STR57## as brick-red crystals. It dyes polyesteran attractive, fluorescent red shade.

EXAMPLE 18

A mixture of 15.2 parts of 4-methoxy salicylaldehyde, 15.7 parts of2-cyanomethyl benzimidazole, 0.3 part of piperidine and 150 parts ofmethanol is stirred at room temperature for 16 hours. The crystalline,greenish-yellow precipitate of iminocoumarin ##STR58## is filtered,washed with methanol and dried.

EXAMPLE 19

12.2 Parts of ethoxymethylenemalodinitrile are added to a boilingmixture of 29.1 parts of the iminocoumarin described above and 100 partsof chlorobenzene. The resulting clear red-brown solution is simmered for5 minutes. On cooling, dyestuff of the formula ##STR59## separates asorange-red prisms. It gives a full reddish-yellow shade on polyester.

EXAMPLE 20

A solution of 14.7 parts of 1,1-dichloro-2,2-dicyanoethylene in 100parts of chlorobenzene is added to a boiling solution of 33.7 parts of7-diethylamino-3-(p-nitrophenyl)-2-iminocoumarin in 100 parts ofchlorobenzene and the deep red mixture is refluxed for 5 minutes. Oncooling, the dyestuff of the formula ##STR60## separates as deep redcrystals. It is filtered, washed repeatedly with methanol andrecrystallized from chlorobenzene to free it from yellow impurities. Italso dyes polyester a brilliant orange shade.

Examples of other dyes prepared by similar procedures are given in thefollowing table.

    __________________________________________________________________________     ##STR61##                                                                    Example                                                                             X.sub.1           X.sub.2  X.sub.3                                                                           X.sub.4                                                                              Shade                             __________________________________________________________________________    21                                                                                   ##STR62##        N(Et).sub.2                                                                            H   CN     Red                               22                                                                                   ##STR63##        "        "   "      Red                               23    CONHC.sub.3 H.sub.6 OH                                                                          "        "   "      Orange                            24    CONHC.sub.3 H.sub.6 OAc                                                                         N(C.sub.2 H.sub.4 OAc).sub.2                                                           "   "      Orange                            25                                                                                   ##STR64##        N(Et).sub.2                                                                            "   "      Orange- yellow                    26                                                                                   ##STR65##        N(CH.sub.3).sub.2                                                                      "   "      Red                               27                                                                                   ##STR66##        N(Et).sub.2                                                                            "   "      Bluish- red                       28                                                                                   ##STR67##        "        "   "      Bluish- red                       29                                                                                   ##STR68##        "        "   "      Orange- red                       30                                                                                   ##STR69##                                                                                       ##STR70##                                                                             "   "      Red                               31    "                                                                                                ##STR71##                                                                             "   "      Red                               32                                                                                   ##STR72##                                                                                       ##STR73##                                                                             "   "      Orange- red                       33    "                                                                                                ##STR74##                                                                             "   "      Orange- red                       34    "                                                                                                ##STR75##                                                                             "   "      Orange- red                       35    "                                                                                                ##STR76##                                                                             "   "      Orange- red                       36    "                 "        "   COOC.sub.2 H.sub.5                                                                   Orange-                                                                       red                               37    "                                                                                                ##STR77##                                                                             "   CN     Orange- red                       38                                                                                   ##STR78##        N(Et).sub.2                                                                            "   "      Orange                            39                                                                                   ##STR79##        "        "   "      Orange                            40                                                                                   ##STR80##        "        "   "      Orange                            41                                                                                   ##STR81##        "        "   "      Orange                            42                                                                                   ##STR82##        "        "   "      Orange                            43                                                                                   ##STR83##        "        "   COOC.sub.2 H.sub.5                                                                   Orange                            44                                                                                   ##STR84##        "        "   "      Orange                            45                                                                                   ##STR85##        "        "   "      Red                               46                                                                                   ##STR86##        N(CH.sub.3).sub.2                                                                      "   CN     Pink                              47                                                                                   ##STR87##        N(Et).sub.2                                                                            "   "      Red                               48                                                                                   ##STR88##        "        "   "      Red                               49                                                                                   ##STR89##        OEt      "   "      Yellow                            50                                                                                   ##STR90##        OCH.sub.3                                                                              "   "      Yellow                            51                                                                                   ##STR91##        N(Et).sub.2                                                                            CN  "      Violet                            52    "                 "        Cl  "      Red                               53    SO.sub.2 Ph       "        "   "      Orange                            54                                                                                   ##STR92##        "        "   "      Yellow- orange                    __________________________________________________________________________

EXAMPLE 55

A solution of 11.2 parts of 1-chloro-2,2-dicyanoethylene in 50 parts ofchlorobenzene is added to a solution of 25.0 parts ofm-diethylaminophenol in 150 parts of chlorobenzene at room temperaturein about 10 minutes. The resulting deep red-brown mixture is stirred atroom temperature for 1 hour more. Solvent is then removed from thereaction mixture by steam distillation when the product ##STR93##separates as clear red-brown crystalline precipitate. It is filtered,washed and dried. It dyes polyester a fluorescent orange shade.

What I claim is:
 1. A fluorescent pigment consisting of N-substitutediminocoumarin of the general formula I, ##STR94## wherein X₁ is anunsubstituted phenyl or naphthyl, or phenyl or naphthyl substituted bynitro, amino, halogen, lower alkyl or lower alkoxy, linked directly orthrough a --CO or --SO₂ group;X₂ is (a) an amino group which isunsubstituted or mono- or di-substituted by lower alkyl or lower alkylsubstituted by hydroxyl, nitrile, lower alkoxy, phenyl,phenylaminocarbonyloxy, phenoxy, halogen, lower alkoxycarbonyl, oracyloxy selected from benzoyloxy or acetyloxy; or by radicals--CH₂ CH₂OCH₂ CH₂ OH, ##STR95## or --CH₂ ═CH--CH₂ ; or (b) a hydroxy group or analkoxy group; X₃ is a hydrogen atom, a halogen atom or a cyano group andX₄ is a carboxylic acid group which has been esterified by loweralkanol, or a cyano group.
 2. An iminocoumarin compound according toclaim 1 characterised in that X₂ is a dialkylamino group and X₁, X₃ andX₄ have the meanings given under claim
 1. 3. An iminocoumarin compoundaccording to claim 1 characterised in that X₃ is a hydrogen atom or acyano group.
 4. An iminocoumarin compound according to claim 1characterised in that the group X₄ is a cyano group.
 5. The dyestuffaccording to claim 1 of the formula ##STR96##